#div1{
    width: 20em;
    height: 10em;
    border: black solid 1px;
    background-color:red;
}
/*相对定位*/
#div2{
    width: 20em;
    height: 10em;
    border: lawngreen dashed 3px;
    background-color: cadetblue;
    /*margin-left: 10px;    外边距     */
    position: relative;
    left: 1em;
    top: 1em;
}
/*绝对定位*/
#div3{
    width: 20em;
    height: 10em;
    border: blueviolet double 5px;
    background-color: blue;
    position: absolute;
    left: 6em;
    top: 6em;
}
/*固定位置*/
.fixed-side{
    width: 20em;
    height: 10em;
    border: brown double 1px;
    background-color: bisque;
    position: fixed;
    left: 30em;
    top: 10em;
}
/*溢出*/
.one{
    width: 3em;
    height: 30em;
    border: orange solid 3px;
    margin-bottom:10em ;
    overflow: scroll;
    /*overflow: hidden;    溢出：隐藏*/
}

.one,.two,.three{
    width: 2em;
    height: 30em;
    border: black solid 1px;
    margin-bottom: 10em;
    overflow: hidden;
    /*overflow: scroll;*/
    float: left;
}
.clf{
    clear: both;
}
.four{
    float: left;
    width: 30em;
    height: 2em;
    border: black solid 2px;
    background-color: crimson;
    margin-bottom: 3em;
}